/Engine/Plugins/Runtime/CommonUI/Source/CommonUI/Public/Widgets/CommonActivatableWidgetContainer.h
NOTE: In general, it isstronglyrecommended that you opt for the class-based AddWidget above. This one is mostly just here for legacy support.
void AddWidgetInstance ( [UCommonActivatableWidget](API\Plugins\CommonUI\UCommonActivatableWidget) & ActivatableWidget )